Fast response, multiple-loop temperature regulator

Abstract

An apparatus for regulating a temperature of an object to a desired temperature includes a feedback circuit operable to produce a feedback error signal based on a difference of the desired temperature of the object and the temperature of the object; and a heating circuit operable to impart heat to the object as a substantially linear function of a command signal, the command signal being based on the feedback error signal.

What is claimed is:  
     
       1. An apparatus for regulating a temperature of an object to a desired temperature, comprising: 
       a feedback circuit operable to produce a feedback error signal in response to a difference of the desired temperature of the object and the temperature of the object; and  
       a heating circuit operable to impart heat to the object as a substantially linear function of a command signal, the command signal being based on the feedback error signal.  
     
     
       2. The apparatus of  claim 1 , wherein the feedback circuit is operable to produce the feedback error signal in substantial proportion to the difference of the desired temperature of the object and the temperature of the object. 
     
     
       3. The apparatus of  claim 1 , wherein the heating circuit includes: 
       a drive circuit operable to produce at least one of a drive voltage and a drive current in response to the command signal; and  
       at least one active heating component operable to produce the heat as a substantially linear function of the command signal.  
     
     
       4. The apparatus of  claim 3 , wherein: 
       the at least one active heating component is further operable to draw current from a voltage source as a substantially linear function of the command signal;  
       the heating circuit further includes a current detection circuit operable to produce a current feedback signal in proportional response to the current drawn by the at least one active heating component; and  
       the drive circuit is further operable to produce the at least one of the drive voltage and drive current in further response to the feedback current signal to cause the at least one active heating component to produce the heat as a substantially linear function of the command signal.  
     
     
       5. The apparatus of  claim 4 , wherein the heating circuit further includes a power limiting circuit operable to limit the current drawn by the at least one active heating component when the command signal exceeds a threshold. 
     
     
       6. The apparatus of  claim 3 , wherein the at least one drive circuit is operable to change the impedance of the active heating component as a function of the command signal such that it produces heat as a substantially linear function of the command signal. 
     
     
       7. The apparatus of  claim 6 , wherein the at least one active heating component is taken from the group consisting of field effect transistors, MOS-gated field effect transistors, N-channel MOS-gated field effect transistors, bipolar transistors, and insulated gate bipolar transistors. 
     
     
       8. The apparatus of  claim 3 , wherein the at least one active heating component includes at least two transistors operatively connected in a cascode configuration. 
     
     
       9. The apparatus of  claim 8 , wherein the at least two transistors are disposed substantially symmetrically about the object. 
     
     
       10. The apparatus of  claim 8 , wherein the at least two transistors are MOS-gated field effect transistors. 
     
     
       11. The apparatus of  claim 1 , further comprising a feed-forward circuit operable to produce a feed-forward error signal in response to a difference of the desired temperature of the object and a base temperature, wherein the object is in thermal communication with a thermal base that tends to draw the temperature of the object to the base temperature, and the command signal is an aggregate of the feed-forward and feedback error signals. 
     
     
       12. The apparatus of  claim 11 , wherein the feed-forward circuit is further operable to produce the feed-forward error signal in substantial proportion to the difference of the desired temperature of the object and the base temperature. 
     
     
       13. The apparatus of  claim 11 , wherein the heating circuit includes: 
       a drive circuit operable to produce at least one of a drive voltage and a drive current in response to the command signal; and  
       at least one active heating component operable to produce the heat as a substantially linear function of the command signal.  
     
     
       14. The apparatus of  claim 13 , wherein: 
       the at least one active heating component is further operable to draw current from a voltage source as a substantially linear function of the command signal;  
       the heating circuit further includes a current detection circuit operable to produce a current feedback signal in proportional response to the current drawn by the at least one active heating component; and  
       the drive circuit is further operable to produce the at least one of the drive voltage and drive current in further response to the feedback current signal to cause the at least one active heating component to produce the heat as a substantially linear function of the command signal.  
     
     
       15. The apparatus of  claim 14 , wherein the heating circuit further includes a power limiting circuit operable to limit the current drawn by the at least one active heating component when the command signal exceeds a threshold. 
     
     
       16. The apparatus of  claim 13 , wherein the at least one active heating component is operable to change its impedance as a function of the command signal such that it produces heat as a substantially linear function of the command signal. 
     
     
       17. The apparatus of  claim 16 , wherein the at least one active heating component is taken from the group consisting of field effect transistors, MOS-gated field effect transistors, N-channel MOS-gated field effect transistors, bipolar transistors, and insulated gate bipolar transistors. 
     
     
       18. The apparatus of  claim 13 , wherein the at least one active heating component includes at least two transistors operatively connected in a cascode configuration. 
     
     
       19. The apparatus of  claim 18 , wherein the at least two transistors are disposed substantially symmetrically about the object. 
     
     
       20. The apparatus of  claim 18 , wherein the at least two transistors are MOS-gated field effect transistors. 
     
     
       21. The apparatus of  claim 11 , wherein the feed-forward circuit includes: 
       a first temperature sensor operable to produce a first temperature signal in correspondence with the base temperature; and  
       a forward error amplifier circuit operable to produce the feed-forward error signal in response to the first temperature signal and a reference signal representing the desired temperature of the object.  
     
     
       22. The apparatus of  claim 21 , wherein a gain of the feed-forward circuit is inversely proportional to a thermal resistance from the base temperature to the object. 
     
     
       23. The apparatus of  claim 21 , wherein the feedback circuit includes: 
       a second temperature sensor operable to produce a second temperature signal based on the temperature of the object; and  
       a feedback error amplifier circuit operable to produce the feedback error signal in response to the second temperature signal and the reference signal.  
     
     
       24. The apparatus of  claim 23 , wherein the object is a thermally conductive substrate on which an operative circuit is disposed such that a temperature of the operative circuit is regulated to a predetermined temperature by regulating the temperature of the thermally conductive substrate to the desired temperature. 
     
     
       25. The apparatus of  claim 24 , wherein the operative circuit is a microwave frequency oscillator. 
     
     
       26. The apparatus of  claim 25 , wherein thermally conductive substrate is formed of a ceramic material. 
     
     
       27. The apparatus of  claim 25 , wherein the second temperature sensor is in thermal communication with the thermally conductive substrate. 
     
     
       28. The apparatus of  claim 25 , wherein the heating circuit includes at least two transistors operatively connected in a cascode configuration and disposed on the thermally conductive substrate such that the oscillator is substantially between them. 
     
     
       29. The apparatus of  claim 25 , wherein the heating circuit includes at least two transistors disposed substantially symmetrically about the oscillator on the thermally conductive substrate. 
     
     
       30. The apparatus of  claim 28 , wherein the at least two transistors are MOS-gated field effect transistors. 
     
     
       31. The apparatus of  claim 25 , wherein the thermally conductive substrate is disposed on a metal carrier and the metal carrier is thermally coupled to a heat sink. 
     
     
       32. The apparatus of  claim 31 , wherein the heat sink is substantially at the base temperature. 
     
     
       33. The apparatus of  claim 32 , wherein the first temperature sensor is coupled to, and thermally isolated from, the metal carrier. 
     
     
       34. The apparatus of  claim 32 , wherein the first temperature sensor is in thermal communication with the heat sink. 
     
     
       35. An apparatus for regulating a temperature of an object to a desired temperature, the object being in thermal communication with a thermal base that tends to draw the temperature of the object to the base temperature, the apparatus comprising: 
       a feed-forward circuit operable to produce a feed-forward error signal in response to a difference of the desired temperature of the object and the base temperature;  
       a feedback circuit operable to produce a feedback error signal in response to a difference of the desired temperature of the object and the temperature of the object; and  
       a heating circuit operable to impart heat to the object as a substantially linear function of an aggregate of the feed-forward and feedback error signals.  
     
     
       36. A microwave frequency oscillator being in thermal communication with a thermal base that tends to draw a temperature of the oscillator to a base temperature, comprising: 
       a feed-forward circuit operable to produce a feed-forward error signal substantially equal to a difference of a desired temperature of the oscillator and the base temperature;  
       a feedback circuit operable to produce a feedback error signal substantially equal to a difference of the desired temperature of the oscillator and the temperature of the oscillator; and  
       a heating circuit operable to impart heat to the oscillator as a substantially linear function of a command signal, the command signal being an aggregate of the feedback and feed-forward error signals.  
     
     
       37. A method for regulating a temperature of an object to a desired temperature, comprising: 
       producing a feedback error signal in response to a difference of the desired temperature of the object and the temperature of the object; and  
       heating the object as a substantially linear function of a command signal, the command signal being based on the feedback error signal.  
     
     
       38. The method of  claim 37 , further comprising producing a feed-forward error signal in response to a difference of the desired temperature of the object and a base temperature, wherein the object is in thermal communication with a thermal base that tends to draw the temperature of the object to the base temperature, and the command signal is an aggregate of the feed-forward and feedback error signals. 
     
     
       39. The method of  claim 38 , further comprising employing at least one active heating component to heat the object as a substantially linear function of the command signal. 
     
     
       40. The method of  claim 38 , further comprising: 
       producing a first temperature signal in correspondence with the base temperature; and  
       producing the feed-forward error signal in response to the first temperature signal and a reference signal representing the desired temperature of the object.  
     
     
       41. The method of  claim 40 , further comprising producing the feed-forward error signal in proportion to a thermal resistance from the base temperature to the object. 
     
     
       42. The method of  claim 40 , further comprising: 
       producing a second temperature signal based on the temperature of the object; and  
       producing the feedback error signal in response to the second temperature signal and the reference signal.  
     
     
       43. The method of  claim 42 , wherein the object is a thermally conductive substrate on which an operative circuit is disposed, the method further comprising regulating the temperature of the thermally conductive substrate to the desired temperature such that a temperature of the operative circuit is regulated to a predetermined temperature. 
     
     
       44. A method for regulating a temperature of an object to a desired temperature, the object being in thermal communication with a thermal base that tends to draw the temperature of the object to a base temperature, the method comprising: 
       producing a feed-forward error signal substantially proportional to a difference of the desired temperature of the object and the base temperature;  
       producing a feedback error signal substantially proportional to a difference of the desired temperature of the object and the temperature of the object; and  
       heating the object as a substantially linear function of a command signal, the command signal being an aggregate of the feed-forward and feedback error signals.